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Alot of interest always surrounds the 800cc 2-stroke market, but especially the past couple years as manufacturers have launched several new engines. That continues this year with a new direct injected 800 from Ski-Doo and a totally re-vamped Liberty Cleanfire 800 from Polaris. To be sure, the big 800 twins of 2011 are among the best 800 engines (twin or triple) we’ve ever straddled.
The test We were lucky enough to talk with
Jim Czekala, owner of Dynotech Research in Batavia, N.Y., early this summer just as he got his hands on a pre-production Polaris Rush CFI 800. This was one of the same sleds we rode out west in our late-season tests as it was part of Polaris’ demo fleet. So this was well broken in with 1,700 miles on it. Three Seas Polaris in Mayville, N.Y. supplied the sled and racer Casey Mulkins was essential in getting the sled to Dynotech for testing.
In this dyno test standard fresh 93 octane (10% ethanol) was used and the ethanol wires were left unplugged. Several dyno pulls were done and the best of the pulls is what is reflected in our chart and graph. The dyno tests were done with 20-second wide-open-throttle pulls.
Results? The 2011 pre-production Rush mustered 143.2 horsepower at 8100 rpm. Torque was a healthy 96.2 ft.-lbs. at 7600 rpm.
Dynotech Jim points out that it’s apparent from viewing the graph that the exhaust valves are programmed to open much later on the new 2011 800 Rush than what he has seen with the former Polaris 800 Dragons. Jim also noted “this later valve opening adds lots of midrange airflow and horsepower compared to the 2010 Dragon 800s.”
Jim dynoed Casey’s stock 800 Dragon (with all the Polaris service updates done) back-to-back with the 2011 800 Rush and saw that peak horsepower on the updated Dragon engine was 5-7 higher than the 800 Rush. From the data, and data from dynos of other Polaris Dragons, Jim concluded that “a properly tuned new Rush 800 has a midrange horsepower advantage compared to a properly tuned Dragon 800, but further investigation needs to be done to see why the Rush’s top-end airflow and horsepower is lower.”
Conclusions We’re excited that midrange power and torque have not been tamed down in the new Rush 800, and we’re also happy to see that the updates Polaris made over the last year or two to the Dragon 800 seem to be working well to make the horsepower Polaris originally hoped for. Also, while the new 800 Rush did not make the 150+ horses that we are seeing from competing engines in this class, it is important to remember that this dyno session was done with a pre-production unit and things often change before production in October and November.
Furthermore, we always seem to harp on power-to-weight ratios and Polaris and Ski-Doo are the only two OEMs to still be quoting sled-weights. At 464 lbs. dry, the Rush 800 is closing in on the Ski-Doo 800 E-TEC in terms of being the lightweight king. Unfortunately, the F8 is still dozens of pounds heavier than the Rush.
So, will the Rush 800 be competitive in this engine class? Yes! Will it blow the other 800s out of the water? No.